The name given to broken pieces of flint found in rich people'sgarden's, usually around expensive shrubberies. They think it looks exclusive and classy. It's neither.

"I see Daryl's been at work in his garden, laying down all that shiny flint pish."
"Yeah well, it's his garden and he can do what he wants with it I suppose."
"True but that money would have been better spent on something which actually looks nice and doesn't show him up to be a colossal asshole with more money than sense."